LAYER-LAYER LITHIUM RICH COMPLEX METAL OXIDES WITH HIGH SPECIFIC CAPACITY AND EXCELLENT CYCLING
Lithium rich and manganese rich lithium metal oxides are described that provide for excellent performance in lithium-based batteries. The specific compositions can be engineered within a specified range of compositions to provide desired performance characteristics. Selected compositions can provide high values of specific capacity with a reasonably high average voltage. Compositions of particular interest can be represented by the formula, x Li 2 MnO 3 .(1−x) Li Ni u+Δ Mn u−Δ Co w A y O 2 ). The compositions undergo significant first cycle irreversible changes, but the compositions cycle stably after the first cycle.
1 . A positive electrode active material for a lithium ion battery having a room temperature specific discharge capacity from 4.6V to 2V of at least about 210 mAh/g at a discharge rate of C/10 and an irreversible capacity loss of no more than about 60 mAh/g, and comprising a layered lithium metal oxide composition approximately represented by the formula x Li 2 MnO 3 .(1−x) Li Ni u+Δ Mn u−Δ Co w A y O 2 , x is at least about 0.2 and no more than about 0.325, the absolute value of Δ is no more than about 0.3, 2u+w+y is approximately equal to 1, w is in the range from 0 to 1, u is in the range from 0.2 to 0.5 and y is no more than about 0.1, with the proviso that both (u+Δ) and w are not zero, wherein an optional fluorine dopant can replace no more than about 10 mole percent of the oxygen.
2 . The positive electrode active material of claim 1 having an average voltage of at least about 3.625 when discharged from 4.6 volts to 2.0 volts at a rate of C/3.
3 . The positive electrode active material of claim 1 further comprising a stabilization coating.
4 . The positive electrode active material of claim 3 wherein the stabilization coating comprises fluorine.
5 . The positive electrode active material of claim 3 wherein the stabilization coating comprises a metal oxide.
6 . The positive electrode active material of claim 1 wherein the absolute value of Δ is no more than about 0.175, w is at least about 0.1 and no more than about 0.6 and u is at least about 0.225 and no more than about 0.45.
7 . The positive electrode active material of claim 1 having an irreversible capacity loss of no more than about 50 mAh/g and a room temperature specific discharge capacity of at least about 215 mAh/g when discharged from 4.6V to 2V at a rate of C/10.
8 . The positive electrode active material of claim 1 having an irreversible capacity loss of no more than about 45 mAh/g and a room temperature specific discharge capacity of at least about 220 mAh/g when discharged from 4.6V to 2V at a rate of C/10.
9 . A positive electrode active material for a lithium ion cell comprising a layered lithium metal oxide composition approximately represented by the formula Li 1+b Ni α Mn β Co γ A δ O 2−z F z , where b ranges from about 0.091 to about 0.14, α ranges from 0.1 to about 0.4, β range from about 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from about 0 to about 0.15 and z ranges from 0 to 0.2, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof, and having a stabilization coating, wherein when discharged at room temperature at a discharge rate of C/10 the positive electrode active material has a specific discharge capacity of at least about 215 mAh/g from 4.6V to 2V.
10 . The positive electrode active material of claim 9 wherein b+α+β+γ+δ is approximately equal to 1.
11 . The positive electrode active material of claim 9 wherein the stabilization coating comprises fluorine.
12 . The positive electrode active material of claim 9 wherein the stabilization coating comprises a metal oxide.
13 . The positive electrode active material of claim 9 wherein α ranges from 0.1125 to about 0.35 and γ ranges from 0 to about 0.35.
14 . The positive electrode active material of claim 9 having an irreversible capacity loss of no more than about 50 mAh/g.
15 . A method for synthesizing a positive electrode active composition, the method comprising:
co-precipitating a precursor composition comprising manganese as well as nickel and/or cobalt in selected amounts corresponding to a product composition approximately represented by the formula x Li 2 MnO 3 .(1−x) Li Ni u+Δ Mn u−Δ Co w A y O 2 , x is at least about 0.2 and no more than about 0.325, the absolute value of Δ is no more than about 0.3, 2u+w+y is approximately equal to 1, w is in the range from 0 to 1, u is in the range from 0.2 to 0.5 and y is no more than about 0.1 with the proviso that both (u+Δ) and w are not zero, wherein an optional fluorine dopant can replace no more than about 10 mole percent of the oxygen;
adding a lithium source at a selected point in the process;
heating the precursor composition to a first temperature to decompose the precursor composition to form a metal oxide; and
heating the metal oxide to a second temperature greater than the first temperature to improve the crystallinity of the metal oxide wherein the product active composition has a specific discharge capacity of at least about 210 mAh/g cycled from 4.6 volts to 2.0 volts at a rate of C/3.
16 . The method of claim 15 wherein the precursors compositions are in a solution having a pH between about 6.0 and about 12.0.
17 . The method of claim 15 wherein the first temperature between about 400° C. and about 800° C.
18 . The method of claim 15 wherein the second temperature is at least about 650° C.
19 . The method of claim 15 wherein the precursor composition comprises a carbonate.
20 . The method of claim 15 wherein the lithium source is blended with the precursor composition prior to the decomposition of the precursor composition to form the metal oxide.